This patent application claims priority based on Japanese patent applications, H11-067366 filed on Mar. 12, 1999, H11-075129 filed on Mar. 19, 1999, H10-315856 filed on Nov. 06, 1998, H10-314564 filed on Nov. 5, 1998, H11-015293 filed on Jan. 25, 1999, H11-16840 filed on Jan. 26, 1999, H10-314574 filed on Nov. 5, 1998, H11-067199 filed on Mar. 12, 1999, H10-315849 filed on Nov. 6, 1998, H11-010197 filed on Jan. 19, 1999, H11-112354 filed on Apr. 20, 1999, H11-046141 filed on Feb. 24, 1999, H10-314553 filed on Nov. 5, 1998, H11-065819 filed on Mar. 12, 1999, H11-118094 filed on Apr. 26, 1999, H11-044902 filed on Feb. 23, 1999, and H11-064994 filed on Mar. 11, 1999, the contents of which are incorporated herein by reference.
1. Field of Invention
The present invention relates to an optical fiber manufacture method, a preform manufacture method and a preform manufacture apparatus that can manufacture a preform and an optical fiber with reduced variation in their diameters.
2. Description of Related Art
FIG. 1 shows a conventional glass base material first elongating apparatus 400. A glass base material 102, which is a base material of an optical fiber, is usually elongated by the glass base material first elongating apparatus 400. This reduces the diameter of the glass base material 102, to produce a glass rod 106. The glass rod 106 has a diameter from 3 mm to 5 mm larger than the most convenient diameter to draw an optical fiber. The most convenient diameter for drawing an optical fiber is 30 mm to 80 mm.
A glass base material first elongating apparatus 400 comprises a heating furnace 100 that heats the glass base material 102 and a drawing chuck 104 that holds and elongates the heated glass base material 102. To elongate the glass base material 102, the glass base material first elongating apparatus 400 supplies the glass base material 102 to the heating furnace 100. Here the glass base material 102 is heated to approximately 2000xc2x0 C. The first elongating apparatus 400 then holds the glass base material 102 by the drawing chuck 104, and draws the glass base material 102 from the heating furnace 100 downward continuously to form a glass rod 106.
FIG. 2 shows a configuration of a conventional glass lathe 110. The glass rod 106 made by the glass base material first elongating apparatus 400 undergoes secondary elongation by the lass lathe 110 to produce a preform 107. At this time, the diameter of the glass rod 106 is reduced to prescribed diameter. The glass lathe 110 comprises chucks 118 and 119 that hold the glass rod 106, a tail stock 116 which moves the chuck 119, and a heating source 122 which heats the glass rod 106. One side of the chuck 118 is fixed, and the other side of the chuck 119 movable. A traction force can be applied to the chuck 119. The glass rod 106, which is held by the chucks 118 and 119, is heated by the heating source 122. The heated glass rod 106 is elongated by moving the tail stock 116 which pulls the glass rod 106. The result is, the diameter of the glass rod 106 reduces to become the prescribed diameter.
There was the possibility of manufacturing bent glass rods 106 when using a conventional glass base material first elongating apparatus 400 to elongate the glass base material 102. Also, when using a conventional glass lathe 110 to elongate the glass rod 106 to manufacture the preform 107 further problems often arose. These problems included variation in the diameter of the preform 107 because the amount of gas provided to the heating source 122 and the speed of moving the tail-stock 116 differed for each preform 107 produced.
When elongating a bent glass rod 106, which is made by a conventional glass base material first elongating apparatus 400, to make a preform 107 by the glass lathe 110, the diameter of the preform 107 varied. When manufacturing optical fibers by drawing a preform 107 with a varying diameter, the diameter of the optical fibers produced also varies. This makes it difficult to manufacture an optical fiber of high quality.
As stated, it is an object of the present invention to provide an optical fiber manufacture method, a preform manufacture method and a preform manufacture equipment that can solve the problems outlined above. The object of the present invention can be achieved by the combinations of features described in the independent claims of the present invention. The dependent claims define further advantageous embodiments of the present invention.
According to the first aspect of the present invention, a method for manufacturing an optical fiber can be provided which comprises setting a heating condition for heating a glass rod, which is a parent material of the optical fiber, and an elongating speed of the glass rod based on a prescribed numerical value which changes with a progress of elongation of the glass rod; heating and elongating the glass rod to generate a preform based on the heating condition and the elongating speed which are set by the setting; and drawing the preform to a filament-like form by further heating the preform to generate the optical fiber.
A method for manufacturing an optical fiber can be provided such that the setting sets the heating condition and the elongating speed based on a progress time of the elongation as the numerical value. The heating and elongating may include end drawing for reducing a diameter of an end of the glass rod, and the end drawing end-draws the end of the glass rod with heat and elongation based on the progress time of the end drawing.
A method for manufacturing an optical fiber can be provided such that the setting sets a location of a burner, which heats the glass rod, and an amount of gas supplied to the burner as the heating condition based on the progress time of the elongation. The setting may set a moving speed of a chuck, which holds the glass rod, as the elongating speed based on the progress time of the elongation.
A method for manufacturing an optical fiber can be provided such that the setting sets the heating condition and the elongating speed based on an elongation length of the glass rod in the elongation as the numerical value.
A method for manufacturing an optical fiber can be provided such that the heating and elongating includes end drawing for reducing a diameter of an end of the glass rod, and the end drawing end-draws the end of the glass rod with heat and elongation based on the elongation length of the glass rod. The setting may set a moving distance of a burner, which heats the glass rod, and an amount of gas supplied to the burner as the heating condition based on the elongation length of the glass rod. The setting can further set a moving speed of a chuck, which holds the glass rod, as the elongating speed based on the elongation length of the glass rod.
A method for manufacturing an optical fiber can be provided such that the setting uses a encoder, which is provided on a motor that drives the chuck, to measure a moving distance of the chuck by measuring a rotation angle of the motor.
A method for manufacturing an optical fiber can be provided such that the setting sets the heating condition and the elongating speed based on a tensile stress generated on the glass rod in the elongation as the numerical value.
A method for manufacturing an optical fiber can be provided such that a heating source, which heats the glass rod, moves along a longitudinal direction of the glass rod with a progress of the elongation, and the heating and elongating controls the elongating speed so that the tensile stress before the heating source moves prescribed distance becomes substantially 110 percent or below an average value of the tensile stress after the heating source moves the prescribed distance.
A method for manufacturing an optical fiber can be provided such that the heating and elongating controls the tensile stress so that the tensile stress before the heating source moves the prescribed distance become substantially from 80 to 110 percent of an average value of the tensile stress after the heating source moves the prescribed distance.
The prescribed distance can be substantially between 50 mm to 150 mm. The heating and elongating may control the elongating speed to be a constant speed when the heating source moves the prescribed distance. The setting may set a moving speed of a chuck, which holds the glass rod, as the elongating speed based on the tensile stress.
A method for manufacturing an optical fiber can be provided such that the setting sets the heating condition and the elongating speed based on a location of a mark provided on a connection between the glass rod and each of dummy rods, which are welded to each of ends of the glass rod, as the numerical value.
A method for manufacturing an optical fiber can be provided such that the heating and elongating includes end drawing for reducing a diameter of an end of the glass rod, and the end drawing end-draws the end of the glass rod with heat and elongation based on the location of a mark. The setting can set the heating condition and the elongating speed based on a location of a cut provided on a connection between the glass rod and each of the dummy rods as the location of a mark.
A method for manufacturing an optical fiber can be provided such that the setting sets the heating condition and the elongating speed based on a location of a fluorescent paint applied on a connection between the glass rod and each of the dummy rods as the location of a mark.
A method for manufacturing an optical fiber can be provided such that the setting sets the elongating speed at a plurality of locations along axial direction of the glass rod based on a diameter at the plurality of locations along axial direction of the glass rod as the numerical value and the heating condition based on an average value of a diameter at the plurality of locations of the glass rod.
A method for manufacturing an optical fiber can be provided such that a end of the glass rod is end-drawn of which diameter is reduced, and the setting has detecting a location of an end-drawn region where the glass rod is end-drawn based on a diameter at a plurality of locations along axial direction of the glass rod and a change of a length of the glass rod along axial direction of the glass rod by the elongation as the numerical value, and setting a polishing range where the glass rod is polished by a flame based on the location of the end-drawn region and also setting a heating power condition of the flame based on a diameter of the end-drawn region, and the heating and elongating polishes the polishing range of the glass rod by the flame of the heating power condition.
According to the other aspect of the present invention, a method for manufacturing an optical fiber can be provided which comprises heating and elongating a glass rod, which is a parent material of an optical fiber, to generate a preform, drawing the preform with further heating to a filament-like form to generate an optical fiber, and the heating and elongating has pre-heating the glass rod until prescribed region of the glass rod softens, and end drawing the prescribed region for reducing a diameter of the prescribed region and for making an end of the glass rod by further heating and elongating the prescribed region.
A method for manufacturing an optical fiber can be provided such that the end drawing further includes second heating which heats by a flame a region which is more towards a middle side of the glass rod than a center of the prescribed region, a thickness of the flame being smaller than a thickness of the flame of the pre-heating.
According to the first aspect of the present invention, a method for manufacturing a preform, which is a parent material of an optical fiber, can be provided which comprises setting a heating condition for heating a glass rod, which is a parent material of the optical fiber, and an elongating speed of the glass rod based on a prescribed numerical value which changes with a progress of elongation of the glass rod, heating and elongating the glass rod to generate a preform based on the heating condition and the elongating speed which are set by the setting.
A method for manufacturing a preform can be provided such that the setting sets the heating condition and the elongating speed based on a progress time of the elongation as the numerical value.
A method for manufacturing a preform can be provided such that the heating and elongating includes end drawing for reducing a diameter of an end of the glass rod, and the end drawing end-draws the end of the glass rod with heat and elongation based on the progress time of the end drawing. The setting may set the heating condition and the elongating speed based on an elongation length of the glass rod in the elongation as the numerical value. The heating and elongating can include end drawing for reducing a diameter of an end of the glass rod, and the end drawing end-draws the end of the glass rod with heat and elongation based on the elongation length of the glass rod.
A method for manufacturing a preform can be provided such that the setting sets the heating condition and the elongating speed based on a tensile stress generated on the glass rod in the elongation as the numerical value.
A method for manufacturing a preform can be provided such that a heating source, which heats the glass rod, moves along a longitudinal direction of the glass rod with a progress of the elongation, and the heating and elongating controls the elongating speed so that the tensile stress before the heating source moves prescribed distance becomes substantially 110 percent or below an average value of the tensile stress after the heating source moves the prescribed distance.
A method for manufacturing a preform can be provided such that the heating and elongating controls the tensile stress so that the tensile stress before the heating source moves the prescribed distance become substantially from 80 to 110 percent of an average value of the tensile stress after the heating source moves the prescribed distance. The prescribed distance can be substantially between 50 mm to 150 mm. The heating and elongating may control the elongating speed to be a constant speed when the heating source moves the prescribed distance.
A method for manufacturing a preform can be provided such that the setting sets the heating condition and the elongating speed based on a location of a mark provided on a connection between the glass rod and each of dummy rods, which are welded to each of ends of the glass rod, as the numerical value. The heating and elongating can include end drawing for reducing a diameter of an end of the glass rod, and the end drawing end-draws the end of the glass rod with heat and elongation based on the location of a mark.
A method for manufacturing a preform can be provided such that the setting sets the elongating speed at a plurality of locations along axial direction of the glass rod based on a diameter at the plurality of locations along axial direction of the glass rod as the numerical value and the heating condition based on an average value of a diameter at the plurality of locations of the glass rod.
A method for manufacturing a preform can be provided such that an end of the glass rod is end-drawn of which diameter is reduced, and the setting has detecting a location of an end-drawn region where the glass rod is end-drawn based on a diameter at a plurality of locations along axial direction of the glass rod and a change of a length of the glass rod along axial direction of the glass rod by the elongation as the numerical value, and setting a polishing range where the glass rod is polished by a flame based on the location of the end-drawn region and also setting a heating power condition of the flame based on a diameter of the end-drawn region, and the heating and elongating polishes the polishing range of the glass rod by the flame of the heating power condition.
According to the other aspect of the present invention, a method for manufacturing a preform, which is a parent material of an optical fiber, can be provided which comprises pre-heating the glass rod until a prescribed region of the glass rod softens, and end drawing the prescribed region for reducing a diameter of the prescribed region and for making an end of the glass rod by further heating and elongating the prescribed region. The end drawing may further include second heating which heats by a flame a region which is more towards a middle side of the glass rod than a center of the prescribed region, a thickness of the flame being smaller than a thickness of the flame of the pre-heating.
According to the first aspect of the present invention, an apparatus for manufacturing a preform, which is a parent material of an optical fiber, can be provided which comprises a heating source which heats a glass rod, which is a parent material of the preform, an elongating unit which elongates the glass rod, a measurement device for measuring a numerical value which changes with a progress of elongation of the glass rod, and a control unit which controls a heating condition of the heating source and a elongating speed of the elongating unit based on the numerical value measured by the measurement device.
An apparatus for manufacturing a preform can be provided such that the measurement device measures a progress time of the elongation as the numerical value, and the control unit controls the heating condition and the elongating speed based on the progress time of the elongation measured by the measurement device.
An apparatus for manufacturing a preform can be provided such that the measurement device measures a moving distance of the elongating unit which changes with a progress of the elongation as the numerical value, and the control unit controls the heating condition and the elongating speed based on the moving distance of the elongating unit measured by the measurement device.
An apparatus for manufacturing a preform can be provided such that the measurement device measures a tensile stress generated on the glass rod by the elongation as the numerical value, and the control unit controls the heating condition and the elongating speed based on the tensile stress generated on the glass rod measured by the measurement device.
An apparatus for manufacturing a preform can be provided such that the heating source moves along a longitudinal direction of the glass rod with a progress of the elongation, and the control unit controls the elongating speed so that the tensile stress before the heating source moves prescribed distance becomes substantially 110 percent or below an average value of the tensile stress after the heating source moves the prescribed distance.
An apparatus for manufacturing a preform can be provided such that the control unit controls the tensile stress so that the tensile stress before the heating source moves the prescribed distance becomes substantially from 80 to 110 percent of an average value of the tensile stress after the heating source moves the prescribed distance. The prescribed distance can be substantially between 50 mm to 150 mm. The control unit may control the elongating speed to be a constant speed when the heating source moves the prescribed distance.
An apparatus for manufacturing a preform can be provided such that the measurement device measures a location of a mark provided on a connection between the glass rod and each of dummy rods, which are welded to each of ends of the glass rod, as the numerical value, and the control unit controls the heating condition and the elongating speed based on the location of a mark measured by the measurement device.
An apparatus for manufacturing a preform can be provided such that the measurement device measures a diameter at a plurality of locations along axial direction of the glass rod as the numerical value, and the control unit controls the elongating speed at the plurality of locations along axial direction of the glass rod based on a diameter at the plurality of locations along axial direction of the glass rod, and the heating condition based on an average value of a diameter at the plurality of locations.